fix chapter name in SUMMARY.md

The "Programs and Libraries" link in TOC doesn't work, this should fix it.

Add Programs and Libraries chapter (fixes #101)

I'm guessing, question marks indicate where I know I'm guessing.

Replaced the section named 'Compiling Your Program' with an up-to-date example

Fixes a few typos and makes some grammar changes.

Change redox-os/zfs -> redox-os/tfs in maintainers

Replace references to Magnet with pkgutils

improve legibility

Fix two typos in 7.4.3. Rusting properly

Fix typo

Fix typing errors in Ion syntax

Spellfix

typo [TFS]

Mac OS -> macOS

new name of mac's system

Propose three categories names for Redox side projects

Added more concrete documentation for compiling test binaries for redox

Updating macOS cross compilers

In section 3.1 'Preparing Redox', the book suggests using the cross compilers from glendc/gcc_cross_compilers. These no longer work, and are not being used in the bootstrap.sh script from the redox-os/redox repo. This closes redox-os/book#84.

STDOUT would be $identifier

Current output is \$identifier.
Additional quote removed
Additional # stdout added for John example

Update preparing_the_build.md

mdBook uses pulldown-cmark. pulldown-cmark implements CommonMark. CommonMark, unlike Github Markdown, needs a space after # for ATX style headers. See http://spec.commonmark.org/0.27/#atx-headings

Update preparing_the_build.md